[web] Memoize Chat component

Summary:
Memoize Chat component to improve performance as described in:
https://linear.app/comm/issue/ENG-1062/add-memoization-to-chat-component-in-web

Test Plan: Run web app, tested the performance when opening modals and checked if app behavior remains unchanged.

Reviewers: palys-swm, atul, benschac

Reviewed By: palys-swm

Subscribers: ashoat, Adrian, atul, karol-bisztyga, yayabosh

Differential Revision: https://phabricator.ashoat.com/D3877